Linn aerial deer count up 90 percent

The number of Linn County deer counted in the annual aerial survey jumped from 468 last year to 892 this year – a 90 percent increase and the largest number recorded in 15 years.

Linn County residents should not, however, jump to the conclusion that the deer population is on the rise, according to Tom Litchfield, deer biologist for the Department of Natural Resources.

Litchfield said he remains confident that the overall deer population trend, both in Linn County and statewide, is downward.

It would be physically impossible for a deer population to actually increase 90 percent in a single year, Litchfield said.

The increase, he said, is more likely a function of the deer being more visible and in different locations.

The aerial survey yields extremely variable results because deer move around in response to changes in food availability, landscape changes caused by development, pressure from hunters and other predators, snow cover and other factors, according to Litchfield.

That's why, he said, the DNR uses several measures to gauge the deer population including actual harvest statistics, roadkill statistics from the Department of Transportation, annual spotlight surveys conducted in the spring and bowhunter diaries.

This year's actual harvest statistics – 2,273 deer killed in Linn County, down 10.4 percent from last year's harvest of 2,537 – reflects the continuing downward trend in the county's deer population, Litchfield said.

Litchfield said he has not yet received updated roadkill data for Linn County but that statewide data on deer-vehicle collisions per billion miles driven remains on an overall downward trajectory.

Here are the aerial survey counts for Linn County deer in recent years: 2003 – 800, 2004 – 764, 2005 – 357, 2006 – no count, 2007 – 662, 2008 – 414, 2009 – 381, 2010 – 468 and 2011 – 892.